Thin film tansistor array panel and fabricating method thereof

ABSTRACT

A method of forming a thin film transistor array panel is described. The thin film transistor array comprises a substrate, a plurality of scan lines, a plurality of gates a plurality of first bonding pads and a plurality of second bonding pads, wherein the first bonding pads are connected with the scan lines. The first bonding pads and the second bonding pads are formed as a part of the first metal layer. The data lines are extended to electrically connected with the second bonding pads via contact windows.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of a prior application Ser. No.10/707,139, filed Nov. 24, 2003, which claims the priority benefit ofTaiwan application serial no. 92117364, filed Jun. 26, 2003.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates in general to a thin film transistor (TFT) arrayand manufacturing method thereof, and more particularly to a thin filmtransistor array having a high opening rate and fabricating methodthereof.

2. Related Art of the Invention

A thin film transistor (TFT) liquid crystal display (LCD) is constructedof at least a thin film transistor array substrate, a color filter arraysubstrate and a liquid crystal layer. The thin film transistor arraysubstrate is composed of a plurality thin film transistors arranged inan array, in which each one of the thin film transistors are disposedwith a corresponding pixel electrode. The thin film transistor describedabove includes a gate, a channel layer, a drain and a source. The thinfilm transistor is provided as a switching device of the liquid crystaldisplay unit.

The operation principle of the thin film transistor device is similar tothat of a conventional MOS device, in which both of them includes threeterminals (gate, drain and source). In general, a thin film transistordevice can be classified into two types, one is an amorphous silicontype and the other is an poly-silicon type, in which the amorphoussilicon thin film transistor is more fully developed than the others.With respect to an amorphous silicon thin film transistor liquid crystaldisplay (LCD), the process flow of manufacturing thereof at leastincludes forming a gate, a channel layer, a source/drain, a pixelelectrode and a cover layer over the substrate.

FIG. 1 is a top view illustrating a conventional thin film transistorarray, and FIG. 1A to FIG. 1E are cross-sectional views illustrating aprocess flow chart of a method of forming a thin film transistor arraysubstrate.

Referring to FIG. 1 and FIG. 1A, first of all, a substrate 100 isprovided. Next, a first masking process is performed to form a gate 12and a scan line 20 connecting to the gate 12. In the meantime, a bondingpad 24 is formed at the terminal of the scan line 20, and then a gatedielectric layer 50 is formed over the substrate 10.

Referring to FIG. 1 and FIG. 1B, a second masking process is performedto form a channel layer 14 and an ohm contact layer 15 on the gatedielectric layer 50 over the gate 12.

Referring to FIG. 1 and FIG. 1C, a third masking process is performed toform source/drain 16 a/16 b and a data line 22 connecting to the source16 a, and another bonding pad 26 is formed at the terminal of the dataline 22.

Referring to FIG. 1 and FIG. 1D, a fourth masking process is performedto form a patterned cover layer 52 over the substrate 10 for exposingthe drain 16 b. The bonding pad 26 and the gate dielectric layer 50 arelocated at an upper level with respect to the bonding pad 24.

Referring to FIG. 1 and FIG. 1E, a fifth masking process is performed toform a patterned low dielectric photoresist layer 54 over the coverlayer 52 for exposing portions of the drain 16 b and the bonding pads26, 24 (exposure of bonding pad 24 not shown). Then, the gate dielectriclayer 50 on the bonding pad 24 is removed by using the photoresist layer54 as an etching mask. Thereafter, a sixth masking process is performedto form pixel electrode 30 on the photoresist layer 54, and to coverindium zinc oxide (IZO) layers 32, 34 over the surface of the bondingpads 26, 24.

The purpose of forming a low dielectric photoresist layer above thecover layer is to enhance the opening rate of the liquid crystaldisplay. Because of the existence of the low dielectric photoresistlayer, the pixel electrode is extended to cover a portion of the dataline to enhance the opening rate. It is noted that the thickness of thelow dielectric photoresist layer is thick enough, therefore theparasitic capactiance between the pixel electrode and the data line isreduced, and the electrical property of the LCD panel will not beinfluenced.

However, in the method described above, after a patterned cover layer isprovided in a masking process, then another masking process is providedfor patterning the low dielectric photoresist layer. Therefore, one moremasking process is required, and therefore the process is morecomplicated. Moreover, if the above process were to be simplifiedapplying a masking process for patterning the low dielectric photoresistlayer with one etching step, however in the resulting structure thebonding pad 26 would remain exposed and unprotected. Therefore in thesubsequent step, the surface of the bonding pad 26 may get damaged dueto its exposure to the reactant used in the subsequent process, forexample, the developer and the etching chemicals, and also during thesteps of forming a low dielectric photoresist layer 54 and then etchingthe gate dielectric layer 50 above the bonding pad 24.

SUMMARY OF THE INVENTION

Accordingly, one object of the present invention is to provide a thinfilm transistor array substrate and the manufacturing method thereof, tosolve the problems of the conventional process.

It is another object of the present invention to provide a thin filmtransistor array substrate and manufacturing method thereof, forsimplifying the manufacturing process and preventing the bonding padthat is electrically connected to the data line from the damage duringthe manufacturing process.

To achieve these and other advantages and in accordance with the purposeof the invention, as embodied and broadly described herein, the presentinvention provides a manufacturing method for a thin film transistorarray substrate. According to this method, a substrate is provided, aplurality of scan lines and a plurality of gates are formed over thesubstrate, wherein the gates are electrically connecteded to the scanlines on a substrate, and a plurality of first bonding pads and aplurality of second bonding pads are formed over two edges of thesubstrate at the same time, wherein the first bonding pads and the scanlines are electrically connected. Next, a gate dielectric layer isformed over the substrate for covering the scan lines, the gates, thefirst bonding pads and the second bonding pads. Next, a plurality ofchannel layers is formed over the gate dielectric layers of each of thegates. Thereafter, a source/drain is formed on each of the channellayers, and a data line is formed to electrically connect with all thesources on the gate dielectric layers, wherein a terminal of each ofdata lines is extended to every second bonding pads. The gates, thechannel layers and the source/drain constitute a plurality of thin filmtransistors.

In the above enbodiment, preferably a first mask layer and a second masklayer are formed over the gate dielectric layers covering the firstbonding pads and the second bonding pads. Preferably the first masklayer and the second mask layer are formed when forming the source/drainand the data line. Alternatively, the first mask layer and the secondmask layer can be formed when forming the channel layer. Moreover, thefirst and the second mask layer may be comprised of a bilayer structurehaving a top layer and a bottom layer and preferably, the top layer isformed when forming the source/drain and the data line and the bottomlayer is formed when forming the channel layer. Then, a cover layer isformed on the substrate, and a patterned low dielectric photoresistlayer is formed over the cover layer. Next, a photoresist layer isformed over the covering layer partially covering over the two edges ofthe substrate, wherein the photoresist layer comprises a plurality offirst openings, a plurality of second openings and a plurality of thirdopenings. A portion of the cover layer above the drain is exposed withinthe first opening, a portion of the cover layer over the data line isexposed within the second opening, and a portion of the cover layer overthe second bonding pad is exposed within the third opening. Next, usingthe photoresist layer as an etching mask, the portions of the coverlayer and the gate dielectric layer that are not covered by thephotoresist layer are removed. Thus, the drain and the data lineadjacent to the edge of the substrate, and the second bonding padadjacent to the data line are exposed. In the etching step, a portion ofthe first mask layer and the second mask layer disposed over the twoedges of the substrate is also provided as an etching mask. Thus, theportion of the gate dielectric layer over the two edges of the substratethat is not coverd by the first/second mask layer is removed in theetching step, and the first bonding pad and the second bonding pad areexposed. Finally, a plurality of pixel electrodes are formed over thephotoresist layer, and an electrode material layer in the second andthird openings and over the first bonding pad and the second bondingpads, wherein the drain and pixel electrode are electrically connectedvia the first opening. The data line and the second bonding pad areelectrically connected via the second and third openings and theelectrode material layer.

It is to be noted that, if the first mask layer and the second masklayers were formed when forming the channel layer, then the first maskand the second mask layer need to be removed resulting in removal of anupper portion of the gate dielectric layer under the first mask layerand the second mask layer, and thereby thinning or reducing thethickness of the gate dielectric layer. Therefore, the thickness of thegate dielectric layer under the first mask layer and the second masklayer will be less than the thickness of the original gate dielectriclayer.

In accordance with a further object of the present invention, thepresent invention provides a thin film transistor array including aplurality of scan lines, a plurality of first bonding pads, a pluralityof second bonding pads, a gate dielectric layer, a plurality of datalines, a plurality of first mask layers, a plurality of second masklayers, a plurality of thin film transistors, a cover layer, a lowdielectric photoresist layer and a plurality of pixel electrodes. Thescan line is disposed on the substrate. The first bonding pad isdisposed on an edge of the substrate, wherein the first bonding pad iselectrically connected with the scan line. The second bonding pad isdisposed on another edge of the substrate. Moreover, the gate dielectriclayer is disposed on the substrate, and portions of the first/secondbonding pads are exposed within the gate dielectric layer. The data lineis disposed over the gate dielectric layer, wherein the data line isextended to the edge of the substrate and electrically connected withthe second bonding pad. In addition, the first mask layer is disposed onthe gate dielectric layer over the first bonding pad, and a portion ofthe first bonding pad is exposed by the first mask layer. The secondmask layer is disposed on the gate dielectric layer over the secondbonding pad, and a portion of the second bonding pad exposed is exposedby the second mask layer. Moreover, the thin film transistor is disposedover the substrate, wherein each of the thin film transistors includes agate, a source/drain and a channel layer. Each of the gates iselectrically connected to each of the scan lines, and each of thesources is electrically connected with each of the data lines. Each ofthe channel layers is disposed over each of the gate dielectric layersof the gates. The cover layer is disposed over the substrate, and thelow dielectric photoresist layer is disposed over the cover layer. Thepart of two edges of the substrate covered by the first mask layer andthe second mask layer not covered by the low dielectric photoresistlayer remain exposed. The pixel electrode is disposed over the lowdielectric photoresist layer corresponding to the thin film transistors,in which each of the pixel electrodes is electrically connected witheach of the drain.

In the above thin film transistor array, the material of the first masklayer and the second mask layer is same as that of the source/drain andthe data line, also they can be same as that of the channel layer.Moreover, the first mask layer and the second mask layer can becomprised of a bilayer structure having a top layer and a bottom layer,in which the material of the top layer can be same as that of thesource/drain and the data line, and the material of the bottom layer canbe same as that of the channel layer.

In accordance with a further object of the present invention, thepresent invention provides a thin film transistor array including aplurality of scan lines, a plurality of first bonding pads, a pluralityof second bonding pads, a gate dielectric layers, a plurality of datalines, a plurality of thin film transistors, a cover layer, a lowdielectric photoresist layer and a plurality of pixel electrodes. Thescan line is disposed over the substrate. The first bonding pads aredisposed over an edge of the substrate, wherein the first bonding padsare electrically connected with the scan lines. The second bonding padsare disposed over another edge of the substrate. Moreover, the gatedielectric layer is disposed over the substrate, wherein portions of thefirst bonding pads and the second bonding pads are exposed by the gatedielectric layer. The thickness of the gate dielectric layer over theedge of the first bonding pads and the second bonding pads and is lessthan a thickness any other portions of the gate dielectric layer.Moreover, the data line is disposed over the gate dielectric layer,wherein the data lines extended to the edge of the substrate toelectrically connect with the second bonding pads. The thin filmtransistors are disposed over the substrate, wherein each of the thinfilm transistors includes a gate, a source/drain and a channel layer.Each of the gates is electrically connected with each of the scan lines,and each of the sources is electrically connected with each of the datalines. Each of the channel layers is disposed over the each of the gatedielectric layers of the gate. In addition, the cover layer is disposedover the substrate, the low dielectric photoresist layer is disposedover the cover layer. The two edges of the substrate having the firstbonding pads and the second bonding pads are exposed by the lowdielectric photoresist layer. The pixel electrodes are disposed over thelow dielectric photoresist layer corresponding to the thin filmtransistors, wherein each of the pixel electrodes is electricallyconnected with each of the drain.

Accordingly, in the manufacturing method of a thin film transistor arraysubstrate of the present invention, the second bonding pads electricallyconnected to the data line is formed under the gate dielectric layer anddisposed in the first metal layer. Therefore, the problem of thedamaging the second bonding pad as in the case of the conventionalprocess can be effectively resolved.

Moreover, in the present invention, because the first mask layer and thesecond mask layer are provided for protecting the first bonding pads andthe second bonding pads, and therefore only one mask is required forpatterning of the low dielectric photoresist layer and the cover layer,and therefore the process the invention is more simplified compared tothe conventional process, and further, damaging of the first bondingpads and the second bonding pads during the processing can beeffectively prevented.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary, and are intended toprovide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the invention, and are incorporated in and constitute apart of this specification. The drawings illustrate embodiments of theinvention and, together with the description, serve to explain theprinciples of the invention. In the drawings,

FIG. 1 is a top view illustrating a conventional thin film transistorarray;

FIG. 1A to FIG. 1E are cross-sectional views illustrating theprogression steps of the process of fabricating a thin film transistorarray substrate corresponding to the cross-sectional view along lineI-I′ of FIG. 1;

FIG. 2A is a top view illustrating a thin film transistor arrayaccording to a first embodiment of the present invention;

FIG. 2B is a view illustrating the second bonding pad shown in FIG. 2A;

FIG. 3A to FIG. 3H are cross-sectional views illustrating theprogression steps of the process of fabricating a thin film transistorarray substrate corresponding to the cross-sectional view along lineII-II′ of FIG. 2A according to the first embodiment of the presentinvention;

FIG. 4A is a top view illustrating a thin film transistor arrayaccording to the second embodiment of the present invention;

FIG. 4B is a view illustrating the bonding pad shown in FIG. 4A;

FIG. 5 is a top view illustrating another thin film transistor arrayaccording to a second embodiment of the present invention;

FIG. 6A to FIG. 61 are cross-sectional views illustrating theprogression steps of a process of fabricating of a thin film transistorarray substrate corresponding to the cross-sectional views along lineII-II′ of FIG. 4A and FIG. 5 according to the second embodiment of thepresent invention;

FIG. 7 is a top view illustrating another thin film transistor arrayaccording to a third embodiment of the present invention;

FIG. 8A to FIG. 8G are cross-sectional views illustrating theprogression steps of process of fabricating a thin film transistor arraysubstrate according to the third embodiment of the present invention;

FIG. 9 is a cross-sectional view of a thin film transistor array havingan etching stop layer;

FIG. 10 is a cross-sectional view of another thin film transistor arrayhaving an etching stop layer; and

FIG. 11 is a cross-sectional view of another thin film transistor arrayhaving an etching stop layer.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention now will be described more fully hereinafter withreference to the accompanying drawings, in which preferred embodimentsof the invention are shown. This invention may, however, be embodied inmany different forms and should not be construed as limited to theembodiments set forth herein; rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the invention to those skilled in the art. Likenumbers refer to like elements throughout.

Hereinafter, FIG. 2A is a top view illustrating a thin film transistorarray according to the first embodiment of the present invention. FIG.2B is a view illustrating the second bonding pad shown in FIG. 2A. FIG.3A to FIG. 3H are cross-sectional views illustrating the progressionsteps of a process of fabricating a thin film transistor array substratecorresponding to the cross-sectional view along line II-II′ of FIG. 2Aaccording to the first embodiment of the present invention.

A thin film transistor array substrate and the manufacturing methodthereof of the present invention will be described in detail in thefollowings, in which a pixel structure and a portion of the bonding padwill be described referring to the figures.

Referring to FIG. 2A and FIG. 3A, first of all, a substrate 100 isprovided. Next, a first masking process is performed to form a scan line101 and a gate 102 over the substrate 100, wherein the gate 102 isconnected with the scan line 101. Next, a first bonding pad 130 and asecond bonding pad 140 are formed over two edges of the substrate 100.The first bonding pad 130 is electrically connected with the scan line101. The scan line 101, the gate 102, the first bonding pad 130 and thesecond bonding pad 140 are disposed in the first metal layer (M1).

Thereafter, a gate dielectric layer 104 is formed on the substrate 100to cover the scan line 101, the gate 102, the first bonding pad 130 andthe second bonding pad 140. A material of the gate dielectric layer 104includes, for example but not limited to, a silicon nitride or a siliconoxide.

Next, referring to FIG. 2A and FIG. 3B, a second masking process isperformed to form a channel layer 106 and an ohm contact layer 108 onthe gate dielectric layer 104 over the gate 102. A material of thechannel layer 106 includes, for example but not limited to, an amorphoussilicon (a-Si). A material of the ohm contact layer 108 includes, forexample but not limited to, a doped amorphous silicon (n+-Si).

Referring FIG. 2A and FIG. 3C, a third masking process is performed toform a source 110 a, a drain 110 b on the ohm contact layer 108, and adata line 112, wherein the data line 122 is connected with the source110 a. A terminal of the data line 112 extends to the second bonding pad140. The gate 102, the source 110 a, the drain 110 b and the channellayer 106 constitute a thin film transistor 111. Wherein, during thestep of forming the source 110 a, the drain 110 b and the data line 112,a conductive layer 152 is further formed over the gate dielectric layer104 and another scan line 101 a being adjacent to the scan line 101.Hereinafter, the conductive layer 152 is provided as a top electrode ofa pixel storage capacitor. Here, the source 110 a, the drain 110 b, thedata line 112 and the conductive layer 152 are disposed in a secondmetal layer (M2).

Particularly, in the present embodiment, when the second metal layerincluding the source 110 a, the drain 110, the data line 112 and theconductive layer 152 is formed, a first mask layer 132 and second masklayer 142 are formed over the gate insulating layer 104, the firstbonding pad 130 and the second bonding pad 140. Wherein the edges of thefirst/second bonding pad 130/140 are covered at least by thefirst/second mask layers 132/142. For example, in the second bonding pad140 and the second mask layer 142 shown in FIG. 2B, a distance “a” and adistance “b” between the second mask layer 142 and the second bondingpad 140 is larger than 0 or equal to 0. Because a material of thefirst/second mask layer 132/142 include a metal material, the areathereof are preferably not too large, therefore the first/second masklayers 132/142 can be designed in a ring pattern to cover the edge ofthe first/second bonding pads 130/140.

Hereinafter, referring to FIG. 3D, after the second metal layer isformed, a cover layer 113 on the substrate 100 is formed to cover thesecond metal layer, i.e., covering the source, 110 a, the drain 110 b,the data line 112, conductive layer 152 and the first/second mask layers132/142. A material of the cover layer 113 includes, for example but notlimited to, a silicon nitride or a silicon oxide.

Referring FIG. 2A and FIG. 3E, a fourth masking process is performed toform a patterned low dielectric photoresist layer 114 over the substrate100 for covering the cover layer 113 and partially covering the twoedges of the substrate 100 (i.e., partially covering the two edges ofthe first bonding pad 130 and the second bonding pad 140). Moreover, inthe above patterning step, a first opening 116, a second opening 118 anda third opening 120 are formed in the low dielectric photoresist layer114. The first opening 116 is positioned over the drain 110 b. Thesecond opening 118 is positioned over a portion of the data line 112 inthe edge of the substrate 100. The third opening 120 is formed over thesecond bonding pad 140 adjacent to the data line 112. Wherein, athickness of the low dielectric photoresist layer 114 is greater than800 nm, and a method of forming the patterned low dielectric photoresistlayer 114 includes, for example but not limited to, coating aphotoresistance material layer and then patterning the photoresistancematerial layer by a lithography process.

Next, referring to FIG. 2A and FIG. 3F, by using the low dielectricphotoresist layer 114 as an etching mask, portions of the cover layer113 and gate dielectric layer 104 that are not covered by the lowdielectric photoresist layer 114 are removed until portions of the drain110 b, the data line 112 adjacent to the edge of the substrate 100, andthe second bonding pad 140 adjacent to the data line 112 respectivelyare exposed. Moreover, in the etching step, the remaining part of thefirst/second mask layers 132/142 adjacent to the two edges of thesubstrate 100 are also provided as an etching mask, in order to removethe gate dielectric layer 104 that are not covered by the first/secondmask layer 132/142 in the two edges of the substrate 100, and to exposea portion of the first bonding pad 130 and a portion of the secondbonding pad 140.

Referring to FIG. 2A and FIG. 3G, a fifth masking process is performedto form a pixel electrode 122 on a surface over the low dielectricphotoresist layer 114, wherein the pixel electrode 122 is electricallyconnected with the drain 110 b via the first opening 116. During thestep of forming pixel electrode 122, a portion of the electrode materiallayer 124 in the second opening 118 and in the third opening 120 areleft behind electrically connecting with the data line 112 and thesecond bonding pad 140 respectively, therefore the data line 112 and thesecond bonding pad 140 are electrically connected. Then an electrodematerial layer 134/144 is formed on a surface over the first/secondbonding pad 130/140, wherein a coverage area of the electrode materiallayer 134/144 covering over the first/second mask layer 132/142 is atleast equal to the area of the layer 132/142. For example, as shown inFIG. 2B, a distance “c” between the second mask layer 142 and theelectrode material layer 144 is larger than or equal to 0.

Referring FIG. 2A, the pixel electrode 122 formed above covers a portionof the data line 112, in order to enhance the opening rate of the thinfilm transistor array. Moreover, the pixel electrode 112 further coversthe conductive layer 152 and a portion of the scan line 101 a, in orderto construct a pixel storage capacitor. Wherein, the pixel electrode 112and the conductive layer 152 are provided as a top electrode, and thescan line 101 a below is provided as a bottom electrode. The gatedielectric layer between the top electrode and the bottom electrode isproviced as a capacitance dielectric layer, wherein the pixel electrode112 and the conductive layer 152 are electrically connected through anopening 154 formed in the low dielectric photoresist layer and the coverlayer.

Hereinafter, referring to FIG. 3H, a portion of the first/second masklayer 132/142 that is not covered by the low dielectric photoresistlayer 114 and the electrode material layers 134, 144 is removed.

In the present embodiment, since the second bonding pad 140 is formedunder the cover layer 113, and the first and second bonding pads 130,140 are disposed in the first metal layer, the second bonding pad 140 isexposed together with the first bonding pad 130 during the same step ofprocess. Therefore, the damage of the second bonding pad 140 due toexposure thereof to the process reactants as in the case of conventionalprocess can be effectively prevented. Moreover, since the first/secondmask layer 132/142 covers the first/second bonding pad 130/140, andtherefore the cover layer 113 and the low dielectric photoresist layer114 can be patterned at the same time without damaging the first bondingpad 130 and the second bonding pad 140.

The thin film transistor array of the present embodiment as shown inFIG. 1A and FIG. 2E is constituted by the scan line 101, the firstbonding pad 130, the second bonding pad 140, the gate dielectric layer104, the data line 112, the first mask layer 132, the second mask layer142, the thin film transistor 111, the cover layer 113, the lowdielectric photoresist layer 114, the pixel electrode 122 and the pixelstorage capacitor 150.

The scan line 101 is disposed on the substrate 100. The first bondingpad 130 is disposed at an edge of the substrate 100, wherein the firstbonding pad 130 and the scan line 101 are electrically connected. Thesecond bonding pad 140 is disposed over another edge of the substrate100. Moreover, the gate dielectric layer 104 is disposed on thesubstrate 100, and a portion of the first/second bonding pad 134/144 isdisposed within the gate dielectric layer 104. The data line 112 isdisposed on the gate dielectric layer 104, wherein the data line 112 isextended to the edge of the substrate 100 and electrically connectedwith the second bonding pad 140 via the openings 118, 120 and theelectrode material layer 124 formed in the openings 118, 120.

In addition, the first mask layer 132 is disposed on the gate dielectriclayer 104 over the first bonding pad 130, and the first bonding pad 130disposed within the gate dielectric layer 104 is also disposed withinthe first mask layer 132. The second mask layer 142 is disposed on thegate dielectric layer 104 over the second bonding pad 140, and a portionof the second bonding pad 140 exposed by patterning the gate dielectriclayer 104 and the second mask layer 142, wherein the edge of thefirst/second bonding pad 130/140 is at least covered by the first/secondmask layer 132/142. A material of the first/second mask layer 132/142 isthe same as the material of the source/drain 110 a/110 b and data line112.

Furthermore, the thin film transistor 111 is disposed on the substrate100, wherein the thin film transistor 111 is constituted by the gate102, the source/drain 110 a/110 b and the channel layer 106. The gate102 is electrically connected with the scan line 101, and the source 110a is electrically connected with the data line 112. The channel layer106 is disposed on the gate dielectric layer 104 over the gate 102.

The cover layer 113 and the low dielectric photoresist layer 114 aredisposed over the substrate 100. The first mask layer 132, the secondmask layer 142 covering the first bonding pad 130 and the second bondingpad 140 over two edges of the substrate 100 are not covered by the lowdielectric photoresis layer 114 and remain exposed. The pixel electrode122 is disposed over the low dielectric photoresist layer 114corresponding to the thin film transistor 111. The pixel electrode 122is electrically connected with the drain 110 b via the contact window116 disposed in the low dielectric photoresist layer 114 and the coverlayer 113.

The pixel storage capacitor 150 is disposed on the scan line 101 aadjacent to the scan line 101. The scan line 101 a is provided as abottom electrode, and the conductive layer 152 and the pixel electrode112 (electrically connected via the contact window 154) over the scanline 101 a is provided as a top electrode. The gate dielectric layer 104between the top electrode and the bottom electrode is provided as acapacitance dielectric layer.

Hereinafter, a second embodiment of the present invention is described.In addition, in the present invention, if the material of the first masklayer and the second mask layer are comprised of an amorphous siliconmaterial, the first mask layer and the second mask layer can befabricated simutaneously as a single mask layer during the formation ofthe channel layer and the ohm contact layer. On the other hand, if thematerial of the first mask layer and the second mask layer is comprisedof a metal, then the first mask layer and the second mask layer can besimultaneously fabricated during the formation of the second metallayer.

FIG. 4A is a top view illustrating a thin film transistor arrayaccording to the second embodiment of the present invention, and FIG. 4Bis a perspective view illustrating the bonding pad shown in FIG. 4A.FIG. 6A to FIG. 6F are cross-sectional views illustrating theprogression steps of a process of fabricating a thin film transistorarray substrate corresponding to the cross-sectional views along lineII-II′ of FIG. 4A according to the second embodiment of the presentinvention. Likewise, hereinafter, a pixel structure and a portion of thebonding pad of a thin film transistor array will be described in detailreferring to the above figures.

First of all, referring to FIG. 4A and FIG. 6A, a substrate 100 isprovided. A first masking process is performed to form a scan line 101and a gate 102 over the substrate 100, wherein the gate 102 iselectrically connected with the scan line 101. Next, a first bonding pad130 and a second bonding pad 140 are simultaneously formed over twoedges of the substrate 100, wherein the first bonding pad 130 iselectrically connected to the scan line 101. The scan line 101, the gate102, the first bonding pad 130 and the second bonding pad 140 aredisopsed in the first metal layer.

Next, a gate dielectric layer 104 is formed over the substrate 100 tocover the scan line 101, the gate 102, the first bonding pad 130 and thesecond bonding pad 140.

Then, referring to FIG. 4A and FIG. 6B, a second masking process isperformed to form a channel layer 106 and an ohm contact layer 108 overthe gate dielectric layer 104. In the meantime, a first mask layer 232and a second mask layer 242 are formed on the gate dielectric layer 104over the first bonding pad 130 and the second bonding pad 140. An ohmcontact material layer (as numeral 242 a shown in FIG. 6B) is formedover the first mask layer and the second mask layer 242.

The edge of the first/second bonding pad 130/140 is at least covered bythe first mask layer 232 and the second mask layer 242. For example, asshown in FIG. 4B, a distance “a” and a distance “b” between the secondbonding pad 140 and the second mask layer 242 is larger than or equal to0.

Next, referring to FIG. 4A and FIG. 6C, a third masking process isperformed to form a source 110 a and a drain 110 b over the ohm contactlayer 108, and a data line 112 connecting to the source 110 a. Aterminal of the data line 112 is extended to the second bonding pad 140.A thin film transistor 111 is constituted by the gate 102, the source110 a, the drain 110 b and the channel layer 106. During the process offorming the source 110 a the drain 110 b, a portion of the ohm contactlayer 108, or even an upper portion of the channel layer 106 will beremoved. Therefore, the ohm contact material layer (as a numeral 242 ashown in FIG. 6B) will be removed during the process of forming thefirst/second mask layer 242. In addition, during the step of forming thesource 110 a, the drain 110 b and the data line 112, a conductive layer152 is also formed on the gate dielectric layer 104 over the other scanline 101 a adjacent to the scan line 101, which will be provided as atop electrode of a pixel storage capacitor. The source 110 a, the drain110 b, the data line 112 and the conductive layer 152 are disposed in asecond metal layer.

Next, referring to FIG. 6D, after the second metal layer is formed, acover layer 113 is formed on the substrate 100 to cover the second metallayer (including the source 110 a, the drain 110 b, the data line 112and the conductive layer 152).

Referring to FIG. 4A and FIG. 6E, a fourth masking process is performedto form a patterned low dielectric photoresist layer 114 over thesubstrate 100 to cover the cover layer 113 partially covering over thetwo edges of the substrate 100, such that the remaining area of thecover layer 113 not covered by the low dielectric photoresist 114 overthe first bonding pad 130 and the second bonding pad 140 remain exposed.The patterned low dielectric photoresist layer 114 comprises a firstopening 116, a second opening 118 and a third opening 120, wherein thefirst opening 116 is formed over the drain 110 b, the second opening 118is formed over the data line 112 at the edge of the substrate 100 andthe third opening 120 is formed over the second bonding pad 140.

Then, referring to FIG. 4A and FIG. 6E, an etching process is performedusing the low dielectric photoresist layer 114 as a etching mask,portions of the cover layer 113 and the gate dielectric layer 104 thatare not covered by the low dielectric photoresist layer 114 are removeduntil portions of the drain 110 b, the data line 112, and the secondbonding pad 140 adjacent to the data line 112 are are respectivelyexposed. In the above etching step, the first mask layer 232 and thesecond mask layer 242 over the two edges of the substrate 100 is alsoprovided as a etching mask, thus the gate dielectric layer 104 that isnot covered by the first mask layer 232 and the second mask layer 242over the two edges of the substrate 100 is removed, and a portion of thefirst bonding pad 130 and a portion of second bonding pad 140 areexposed.

Referring FIG. 4A and FIG. 6G, a fifth masking process is performed toform a pixel electrode 122 over the low dielectric photoresist layer114, wherein the pixel electrode 122 is electrically connected with thedrain 110 b via the first opening 116. During the step of forming thepixel electrode 122, an electrode material layer 124 is formed into thesecond opening 118 and the third opening 120, and therefore the dataline 112 and second bonding pad 140 are electrically connected. Theelectrode material layer 134/144 respectively connects with the firstbonding pad and the second bonding pad 140.

Likewise, the pixel electrode 112 formed above covers the conductivelayer 152 and a portion of the scan line 101 a forming a pixel storagecapacitor 150.

However, if the etching material used in the etching step of FIG. 6Edoes not have an enough etching selectivity to the amorphous silicon andthe dielectric layer, the etching step may remove a portion of the firstmask layer and the second mask layer 242 that is not covered by the lowdielectric photoresist layer 114, or an upper portion of the gatedielectric layer 104 under the first mask layer 232 and the second masklayer 242 as shown in FIG. 6H may be removed. But, with considerableetching selectivity between the amorphous silicon and dielectricmaterial, etching of the gate dielectric layer 104 may be effectivelyprevented the thickness of the gate dielectric layer 104 may bepreserved. Then the fifth masking process is performed to form the pixelelectrode 122 and the electrode material layers 124, 134, 144 as shownin FIG. 61. Therefore, even though the etching stop ability of thefirst/second mask layer 232/242 of the amorphous silicon material layeris not as good enough as that of the metal material, but the etchingselectivity of the amorphous silicon material layer inbetween thedielectric material is still sufficient to prevent the surface of thefirst/second bonding pad 130, 140 from getting the damage due toexposure to etchants during the etching step.

Because of the transparency of the amorphous silicon material is muchlarger than that of the metal material, by using the amorphous siliconmaterial as the first/second mask layer, the first/second mask layer canbe disopsed in a ring pattern (as shown in FIG. 4A) as described above.Moreover, the amorphous silicon layer can be formed covering over thetwo edges of the substrate that are not covered by the low dielectricphotoresist layer 144, and only a portion corresponding to thefirst/second bonding pad 130/140 remain exposed, as shown in FIG. 5.

Referring to FIG. 5, the cross-sectional views taken along line 11-11′in FIG. 5 is shown in FIG. 6A to FIG. 61. The process steps offabricating thin film transistor shown in FIG. 5 is similar to FIG. 4Aexcept that, when performing the second masking process, the design ofthe mask pattern used is different. That is, the second masking processof FIG. 5 further includes disposing the first/second mask layer 332/342at the two edges of the substrate 100 except for forming the channellayer 106 and the ohm contact layer 108. The first/second mask layer332/342 is a rectangular pattern and covers on the two edges of thesubstrate 100 which is not covered by the low dielectric photoresistlayer 114. The opening 332 a/342 a is disposed in the first/second masklayer 332/342, and a first/second bonding pad 130/140 is exposedtherewithin.

In other words, in the process steps of fabricating the thin filmtransistor shown in FIG. 5 is similar to that shown FIG. 4A except thatthe second masking process is different, while the other four maskingprocesses are same.

In the second embodiment, instead of forming the first/second mask layeras a ringed pattern (as shown in FIG. 4A), or as rectangular pattern tocover the two edges of the substrate not covered by the low dielectricphotoresist layer (as shown in FIG. 5), a whole mask layer of thechannel and the ohm contact material is formed. As shown FIG. 7, thebonding pad is hollowed out, and the numeral 600 represents the channeland the ohm contact material layer, and the openings 600 a, 600 b areformed for exposing the bonding pad 140 and 130. In the meantime, thechannel 106 of the thin film transistor 111 does not have a channelpattern, instead the channel and ohm contact material layer 600 betweenthe source 110 a and the drain 110 b are provided as a channel 106.

Moreover, when the whole mask layer 600 of the channel and the ohmcontact material is provided as the first/second mask layer, after theetching process of the final bonding pad, the gate dielectric layer withthe silicon nitride material corresponding to the opening 600 a, 600 bof the mask layer 600 will be totally etched, and the bonding pad 130,140 will be exposed. Likewise, the thickness of the gate dielectriclayer over the bonding pad 130, 140 that is covered by the mask layer600 will be thinner.

Therefore, the thin film transistor (TFT) array manufactured by themethod of the second embodiment has a structure that is similar to thatof the first embodiment except that the first mask layer 332 and thesecond mask layer 342 covers the two edges of the substrate 100 that isnot covered by the low dielectric photoresist layer 144. In anotherembodiment, except for the material of the mask layer 600 including anamorphous silicon material, the mask layer 600 covers the whole surfaceof the substrate 100, while only a portion corresponding to thefirst/second bonding pad 130/140 is exposed.

Moreover, if in the present embodiment, the first/second mask layer232/242 (or layer 332/342, 600) is removed in the etching process, anupper portion of the gate dielectric layer 104 will also be removed, andthe structure will be different from the above structure. The structureof the thin film transistor is described as follows.

The thin film transistor array is constituted by a scan line 101, afirst bonding pad 130, a second bonding pad 140, a gate dielectric layer104, a data line 112, a thin film transistor 111, a cover layer 113, alow dielectric photoresist layer 114, a pixel electrode 122 and a pixelstorage capacitor 150.

The scan line 101 is disposed on the substrate 100. The first bondingpad 130 is disposed over an edge of the substrate 100, wherein the firstbonding pad 130 is electrically connected with the scan line 101. Thesecond bonding pad 140 is disposed over another edge of the substrate100. Moreover, the gate dielectric layer 104 is disposed over thesubstrate 100, wherein a portion of the first bonding pad 130 and thesecond bonding pad 140 are exposed within a opening in the gatedielectric layer 104, and wherein the remaining portions of the firstbonding pad 130 and the second bonding pad 140 remain covered by thegate dielectric layer 104. The thickness of the gate dielectric layer104 that covers the edge of the first bonding pad 130 and the secondbonding pad 140 is less than the thickness of the gate dielectric layer104 in the pixel area. Moreover, the data line 112 is disposed over thegate dielectric layer 104, and the data line 112 extended to the edge ofthe substrate 100 and is electrically connected with the second bondingpad 140 via the openings 118, 120 and the electrode material layer 124formed in the openings 118, 120.

The thin film transistor 111 is disposed over the substrate, wherein thethin film transistor 111 is constituted by a gate 102, a source 110 a, adrain 101 b and a channel layer 106. The gate 102 is electricallyconnected to the scan line 101, and the source 101 a is electricallyconnected to the data line 112. The channel layer 106 is disposed on thegate dielectric layer 104 over the gate 102. In addition, the coverlayer 113 is disposed over the substrate 100, and the low dielectricphotoresist layer 114 is disposed over the cover layer 113. The twoedges of the substrate 100 where the first bonding pad 130 and thesecond bonding pad 140 are disposed remain exposed. The pixel electrode122 is disposed over the low dielectric photoresist layer 114 over thearea corresponding to the disposed thin film transistor 111. The pixelelectrode 122 is electrically connected to the drain 101 b. The pixelstorage capacitor 150 is disposed over the other scan line 101 aadjacent to the scan line 101.

Hereinafter, a third embodiment of the present invention will bedescribed. In the present invention, instead of using the second metallayer or the channel material layer (amorphous silicon layer) forforming the first mask layer and the second mask layer, the first/secondmask layer may also be formed using a combination of the second metallayer combined and the amorphous silicon layer. In other words, whenperforming the second masking process and the third masking process, thepattern of the first/second mask layer is also formed simutaneously, thedetailed process will be describrd as follows.

Hereinafter, FIG. 8A to FIG. 8G are cross-sectional views illustratingthe progression steps of a process of fabricating a thin film transistorarray substrate according to the third embodiment of the presentinvention.

The third embodiment is a combination of the first embodiment and thesecond embodiment. In other words, the first/second mask layer is abilayer structure, in which the material of the top layer 142 is same asthat of the source 1110 a, the drain 1110 b and the data line 112, whilethe material of the bottom layer 242 is same as that of the channellayer 106.

In FIG. 8A to FIG. 8G, the parts that are similar in the two (second andthird) embodiments described above are represented by the same numeral,and the process steps illustrated in FIG. 8A to FIG. 8G are same for thetwo embodiments, except that, when the channel layer 106 is formed, thebottom layer 242 of the first/second mask layer on the gate dielectriclayer 104 over the first/second bonding pad 130/140 is also formedsimutaneously, as shown in FIG. 8B. And when the second metal layer(including the source 1110 a, the drain 1110 b, data line 112 and theconductive layer 152) are formed, the top layer structure 142 of thefirst/second mask layer is also formed smutaneously, as shown in FIG.8C.

Therefore, the steps of forming the cover layer 113, the low dielectricphotoresist layer 114 and the pixel electrode 112 are same for thesecond and the third embodiments described above.

However, it is to be noted that, in the third embodiment, thefirst/second mask layer is comprised of a combination of the secondmetal layer with the amorphous silicon layer can also include othercombinations. For example, the width of the top metal layer can be lessthan that of the bottom amorphous silicon layer, or the width of the topmetal layer can be larger than that of the bottom amorphous siliconlayer. The only requirement is that the edge of the first/second bondingpad must be covered by at least one of the top metal layer or the bottomamorphous silicon layer.

Moreover, the combinations described above may also include disposingthe second metal layer material over a portion of the first/secondbonding pad as a mask layer, and disposing the amorphous siliconmaterial over the other portion of the first/second bonding pad asanother mask layer. Alternatively, a portion of the mask layer disposedover each one of the bonding pad is constituted by the second metallayer material, and the other portion is constituted by the amorphoussilicon layer. The only requirement is that the mask layer constructedby any one or both of the second metal layer material and the amorphoussilicon layer at least covers the edge of the first/second bonding pad.

The manufacturing method of the thin film transistor array substrate ofthe present invention is also suitable for the manufacturing a channellayer having an etching stop layer, the detailed process is described asfollows.

Referring to FIG. 9, after forming a gate dielectric layer 104, achannel layer 106, an etching stop layer 800 and an ohm contact layer108 are formed on the gate dielectric layer 104. Then, a second metallayer is formed over the substrate and patterned until the etching stoplayer 800 is exposed to form a source 1110 a, a drain 1110 b and a dataline 112. While the other process steps are similar to the process stepsdescribed above. For example, in FIG. 9, the method of using a secondmetal layer as a first/second mask layer is similar to the methoddescribed in the first embodiment. And in FIG. 10, the method of usingan amorphous silicon material as a first/second mask layer is similar tothe method described in the second embodiment. And in FIG. 11, themethod of using a second metal layer combined with an amorphous siliconmaterial as a first/second mask layer is similar to the method describedin the second embodiment. In other words, in a manufacturing process ofa thin film transistor having etching stop layer of the presentinvention, the steps of forming the first/second mask layer can beprovided by any one of the three embodiments described above.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the structure of the presentinvention without departing from the scope or spirit of the invention.In view of the foregoing, it is intended that the present inventioncover modifications and variations of this invention provided they fallwithin the scope of the following claims and their equivalents.

1. A method for fabricating a thin film transistor (TFT) arraysubstrate, comprising: providing a substrate; forming a plurality ofscan lines and a plurality of gates electrically connected to said scanlines on the substrate; simultaneously forming a plurality of firstbonding pads and a plurality of second bonding pads over two edges ofthe substrate, wherein said first bonding pads are electricallyconnected with said scan lines; forming a gate dielectric layer over thesubstrate, for covering said scan lines, said gates, said first bondingpads and said second bonding pads; forming a plurality of channel layersover said gate dielectric layers of each of said gates; forming an ohmcontact layers on each of said channel layers; forming a source and adrain on each of the said contact layers; forming a data lineelectrically connecting to each of said sources on the gate dielectriclayers, wherein a terminal of each of said data lines is extended toeach of the second bonding pads, and wherein said gates, each of saidchannel layers and each of said sources and each of said drainconstitute a of thin film transistor; forming a mask layer over saidgate dielectric layers, wherein said mask layer is disposed over areascorresponding to said first bonding pads and said second bonding pads;forming a cover layer over said substrate; forming a patternedphotoresist layer over said cover layer, wherein said photoresist layerpartially covering over said two edges of the substrate, wherein saidphotoresist layer comprises a plurality of first openings, a pluralityof second openings and a plurality of third openings, wherein saiddrains are exposed within said first openings, said data lines areexposed within said second openings, and said second bonding pads areexposed within said third openings; performing an etching process byusing the photoresist layer as an etching mask for removing portions ofsaid cover layer and portions of said gate dielectric layers that arenot covered by the photoresist layer and exposing a portion of saidsecond bonding pads that are not covered by said photoresist layer; andforming an electrode material layer over said photoresist layer to forma plurality of pixel electrodes over said photoresist layer, whereinsaid electrode material layer fills in each of said first openings, saidsecond openings and said third openings, and wherein said drains areelectrically connected with said pixel electrodes via the firstopenings, said data lines are electrically connected with said secondbonding pads via said second openings, said third openings and saidelectrode material layer.
 2. The method of claim 1, wherein siad masklayer is formed during the step of forming said source, said drain andsaid data lines, or during the step of forming said channel layers andsaid ohm contact layers, or by a combination of said steps thereof. 3.The method of claim 2, wherein said mask layer comprises a ring pattern,and covers a pherpheral area over said first bonding pads and saidsecond bonding pads.
 4. The method of claim 2, wherein said mask layerlayer is formed during the step of forming said channel layers and saidohm contact layers, and wherein said mask layer comprises a plurality ofopenings having rectangular block patterns covering over said two edgesof the substrate.
 5. The method of claim 2, wherein said mask layer isformed during the step of forming said channel layers and said ohmcontact layers, wherein said mask layer comprises a plurality ofopenings covering the whole substrate, and wherein a portion of saidgate dielectric layer covering said first bonding pads and said secondbonding pads is exposed within said openings.
 6. The method of claim 2,wherein said mask layer is formed during the step of forming saidchannel layers and said ohm contact layers, and in the step of removingsaid cover layer and said gate dielectric layer that are not covered bythe photoresist layer by using the photoresist layer as an etching mask,and removing an upper portion of of said mask layer.
 7. The method ofclaim 1, wherein said mask layer comprises a bilayer structure having atop layer and a bottom layer, wherein said top layer is formed duringthe step of forming said source, said drain and said data lines, andsaid bottom layer is formed during the step of forming said channellayers and said ohm contact layers.
 8. The method of claim 1, whereinbefore the step of forming said ohm contact layers, further comprises astep of forming an etching stop layer over each of said channel layersover each of said gates.